<!DOCTYPE html>
<html>
<head>
	<title></title>
	<style type="text/css">

.main {
	background: #000;
	width: 500px;
	height: 200px;
	margin: 0 auto; 
	max-width: 600px;
}
/*水平居中显示，屏幕变窄后折叠显示*/
.box {
	width: 500px;
	height: 200px;
	margin: 0 auto;
	max-width: 500px;
	border: solid black 1px;
	 -webkit-box-sizing: border-box;
		-mos-box-sizing: border-box;
			-box-sizing: border-box;
}
/*盒子模型，且让padding无法撑大盒子*/
<button></button>
<ins></ins><del></del>
<map name=""></map>
	</style>
</head>
<body>
<div class="main"></div>
<div class="box"></div>

</body>
</html>